This invention relates generally to automated placement of small electronic components. More particularly, this invention relates to the use of a heated end effector on placement systems to preheat an adhesive on electronic components.
xe2x80x9cChip shootersxe2x80x9d or xe2x80x9cPick-and-Placexe2x80x9d machines rapidly place components such as resistors, capacitors and integrated circuit packages on a circuit board. The placement of components on the board can reach rates of more than 40,000 chips per hour. These machines pick up and accurately locate the component on the end of a vacuum nozzle. Chip shooters use one of two basic designs to place components. The most common is a turret drive with multiple heads around the outside of the turret A feeder carriage is place in the back of the machine that moves back and forth to put the correct component under the turret. As the turret spins, the component is picked up from the feeder carriage and is brought to the front for placement. The advantage of the turret design is speed since many components can be on the turret in process at the same time. The circuit board being assembled moves around under the front of the turret to position the component correctly. A second type of chip shooter is a gantry system. The circuit board is held stationary, or moved in only one axis, and the head goes to the feeder to get the component and moves to the proper location for placement.
When placing flip chip integrated circuits that are pre-coated with an underfill, solder flux or solder paste is not used to hold the chip in place during reflow, as with typical surface mount components. Instead the pre-applied underfill material needs to be heated to soften the material and create a tacky surface to hold the chip in place as the board is transported into the reflow oven. Novel techniques such as a soft beam laser, radiant or ultraviolet heating for the softening step after component pick and placement are being discussed as a potential techniques for heating up the flip chip. However, these techniques have not been proven to be effective for mass production. An alternative approach is to heat the board with infra-red energy prior to entering the placement cell. While this technique can easily be integrated in an existing pick and place platform, it causes the solder paste on the printed circuit boards to dry out. Therefore a method of heating the die during the pick and place step is highly desirable to provide a complete solution for the implementation of the precoated chip in high volume manufacturing.